This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Animals assigned to this project have been successfully infected with a primate lentivirus. The purpose is to continue clinical, virologic and immunologic monitoring for an extended period of time. The current animals have been infected with HIV-1 over 17 years at this time, and all continue to demonstrate seropositive responses to HIV-1 proteins. This indication of continuing but controlled HIV-1 replication has led us to design an experiment to examine the role of CD8+ cells in virus control by temporarily depleting CD8+ cells in vivo by treatment with the humanized mouse monoclonal anti-CD8 antibody, cM-T807. Generally, CD8-depleted virus-controlling macaques experience a coincident marked increase in virus replication and then regain control when CD8+ cells return to pretreatment levels.